The 300 HAM’R is an incredibly efficient modern intermediate cartridge developed by Bill Wilson of Wilson Combat to optimize terminal ballistics from the AR-15 platform! Designed in 2018 and formally accepted by SAAMI in 2020, it takes the 223 Remington parent case and necks it up to accept standard 308-thousandths-inch hunting bullets! By utilizing a specialized case geometry and a sharp 30-degree shoulder, it maximizes powder capacity and operates at a higher pressure than the 300 Blackout, offering hunters unparalleled supersonic performance and knockdown power on deer and feral hogs!
300 HAM’R Case Dimensions Overview
| Dimension Property | Specification (Imperial) | Specification (Metric) |
| Parent Case | 223 Remington | 5 and 56 hundredths mm NATO |
| Bullet Diameter | 308 thousandths in | 7 mm and 82 hundredths |
| Case Length | 1 inch and 603 thousandths | 40 mm and 72 hundredths |
| Case Trim Length | 1 inch and 590 thousandths | 40 mm and 39 hundredths |
| Overall Length (COAL) | 2 inches and 260 thousandths (Max) | 57 mm and 40 hundredths |
| Rim Diameter | 378 thousandths in | 9 mm and 60 hundredths |
| Rim Thickness | 45 thousandths in | 1 mm and 14 hundredths |
| Base Diameter | 376 thousandths in | 9 mm and 55 hundredths |
| Shoulder Diameter | 366 thousandths in | 9 mm and 30 hundredths |
| Neck Diameter | 332 thousandths in | 8 mm and 43 hundredths |
| Shoulder Angle | 30 degrees | 30 degrees |
| Case Capacity | Approx 29 and a half grains water | 1 cubic cm and 92 hundredths |
| Maximum Average Pressure | 57-thousand 500 psi | 396 megapascals |
Understanding the 300 HAM’R Case Dimensions
- Parentage: Derived directly from the ubiquitous 223 Remington case but features a longer powder column and a neck expanded to seat traditional 30-caliber hunting projectiles;
- Shoulder Positioning:Incorporates a 30-degree shoulder angle that is pushed slightly forward compared to the 300 Blackout, preventing dangerous cross-chambering while maximizing internal volume;
- AR-15 Optimization: Engineered to function flawlessly within standard AR-15 magazines and standard 5-56 bolt carriers, requiring only a simple barrel swap to upgrade the entire rifle;
- Action Compatibility: Limits its maximum overall length to 2 inches and 260 thousandths to feed reliably from semi-automatic platforms without modification!
300 HAM’R Case Dimensions in Inches and Millimeters
| Measurement Point | Max (Inches) | Min (Inches) | Max (Millimeters) | Min (Millimeters) |
| Case Length | 1 and 603 thousandths | 1 and 588 thousandths | 40 and 72 hundredths | 40 and 34 hundredths |
| Trim-To Length | 1 and 590 thousandths | None | 40 and 39 hundredths | None |
| Rim Diameter | 378 thousandths | 368 thousandths | 9 and 60 hundredths | 9 and 35 hundredths |
| Base Diameter | 376 thousandths | 369 thousandths | 9 and 55 hundredths | 9 and 37 hundredths |
| Shoulder Diameter | 366 thousandths | 356 thousandths | 9 and 30 hundredths | 9 and 4 hundredths |
| Neck Diameter | 332 thousandths | 322 thousandths | 8 and 43 hundredths | 8 and 18 hundredths |
| Bullet Diameter | 309 thousandths | 306 thousandths | 7 and 85 hundredths | 7 and 77 hundredths |
| Overall Length (COAL) | 2 and 260 thousandths | 2 and 165 thousandths | 57 and 40 hundredths | 54 and 99 hundredths |
300 HAM’R Case Length
The maximum case length of the 300 HAM’R is 1 inch and 603 thousandths (40 mm and 72 hundredths), with a highly recommended trim-to length of 1 inch and 590 thousandths (40 mm and 39 hundredths)!Because it operates at a relatively high pressure of 57-thousand 500 psi, brass will inevitably flow and stretch during normal semi-automatic firing cycles! Handloaders must routinely measure and trim their brass to prevent the neck from pinching inside the chamber and causing dangerous pressure spikes!
300 HAM’R Base and Rim Dimensions
The 300 HAM’R proudly shares the exact same base and rim architecture as its 223 Remington parent case!
- Rim Diameter: 378 thousandths in (9 mm and 60 hundredths)
- Base Diameter: 376 thousandths in (9 mm and 55 hundredths)
- Rim Thickness: 45 thousandths in (1 mm and 14 hundredths)
Because these critical dimensions remain entirely untouched, the cartridge utilizes standard 5-56 NATO bolt carrier groups, making it one of the easiest and most cost-effective heavy hunting upgrades for the modern sporting rifle platform!
300 HAM’R Shoulder and Neck Dimensions
- Shoulder Angle: A steep 30-degree angle ensures a crisp headspace datum line and maximizes the combustion chamber geometry;
- Shoulder Diameter: Measures 366 thousandths in at the junction where the case body meets the shoulder;
- Neck Length & Diameter:Features a robust neck diameter of 332 thousandths in, engineered specifically to securely tension hunting-weight 30-caliber bullets ranging from 110 to 150 grains!
300 HAM’R Case Capacity
The internal case capacity of the 300 HAM’R averages an impressive 29 and a half grains of water, though this can fluctuate slightly depending on the specific brass manufacturer like Starline or Sig Sauer! This internal volume is noticeably larger than the 300 Blackout, allowing the HAM’R to take full advantage of medium-fast rifle powders like Shooters World Blackout, Hodgdon CFE Black, and Accurate 1680! This extra powder capacity pushes a 130-grain bullet roughly 150 to 200 feet per second faster than competing AR-15 utility cartridges!
300 HAM’R Dimensions vs Similar Cartridges
| Cartridge | Bullet Diameter | Case Length | COAL | Max Pressure |
| 300 HAM’R | 308 thousandths | 1 and 603 thousandths | 2 and 260 thousandths | 57-thousand 500 psi |
| 300 Blackout | 308 thousandths | 1 and 368 thousandths | 2 and 260 thousandths | 55-thousand psi |
| 223 Remington | 224 thousandths | 1 and 760 thousandths | 2 and 260 thousandths | 55-thousand psi |
| 350 Legend | 355 thousandths | 1 and 710 thousandths | 2 and 260 thousandths | 55-thousand psi |
| 30-30 Winchester | 308 thousandths | 2 and 390 thousandths | 2 and 550 thousandths | 42-thousand psi |
Chamber and Case Dimensions
The chamber specifications for the 300 HAM’R are optimized strictly for supersonic hunting bullets rather than heavy subsonic projectiles!Because the cartridge features a longer case body and a forward-pushed shoulder compared to the 300 Blackout, it absolutely cannot chamber 300 Blackout ammunition! Furthermore, the throat geometry is tailored to cleanly accommodate spitzer and flat-nose hunting bullets while keeping the overall cartridge length short enough to fit effortlessly inside standard magazines!
Common Questions
- Can I form 300 HAM’R brass from 223 Remington cases?Yes; because the base dimensions are fundamentally identical, many reloaders form custom brass by trimming standard 5-56 NATO or 223 Remington cases down near 1 inch and 603 thousandths, running them heavily lubricated through a full-length 300 HAM’R sizing die, and finally trimming to the precise target length!
- What is the standard twist rate for 300 HAM’R dimensions?A 1 in 15 twist rate is famously utilized by Wilson Combat for this cartridge, providing perfect gyroscopic stability for 110-grain to 150-grain supersonic bullets, while SAAMI also recognizes a standard 1 in 12 twist for testing barrels!
- Why does it have a larger case capacity than 300 Blackout?The brilliant engineers pushed the 30-degree shoulder significantly further forward, extending the cylindrical powder column to hold roughly 3 more grains of water capacity compared to the Blackout!